Conversion of hydrocarbons



H. V. ATWELL Jan. 31, 1939.

CONVERSION OF HYDROCARBONS Filed July 29, 1937 ATTORNEY Patented Jan.3l, 1939 UNITED STATES PATENT oFFlcE CONVERSION OF HYDROCRBONSApplication July 29, 1937, Serial No. l56,272

i Claims.

My invention relates in general to the conversion of normally gaseoushydrocarbons and more particularly to a unitary process for theproduction .of normally liquid hydrocarbons suitable for use as motorfuel from lighter gaseous hydrocarbons such as ethylene.

It has been shown that normally gaeous hydrocarbons can be polymerizedunder suitable conditions to yield normally liquid products. In

w general, however, such known processes of either lili tcularlydirected to the processing of the higher molecular Weight hydrocarbons.

A principal object of my invention is to provide a. unitary processwherein normally gaseous hydrocarbons predominating in ethylene areconverted to normally liquidproducts suitable for use as motor fuel.

A further object of my invention is to provide a unitary process for theconversion of normally gaseous hydrocarbons comprising substantialamounts of ethylene to normally liquid products lill wherein theethylene is initially converted, in the 35 presence of a suitablepromoter, to unsaturated hydrocarbons of higher molecular weight andwherein normally gaseous hydrocarbons comprising unsaturatedhydrocarbons of higher molecular weight so produced aresubjected topolymerizing conditions of temperature and pressure toefect theconversion of normally gaseous hydrocarbons to normally liquid productssuitable as motor fuel.

Another object of my invention is to provide a unitary process for thepolymerization of normally gaseous hydrocarbons wherein normally gaseoushydrocarbons comprising both saturated and unsaturated hydrocarbons areconverted to normally liquid products and wherein ethylene, heretoforefound diicult to convert because of its apparent refractoriness, isconverted in continuous stream to unsaturated hydrocarbons of highermolecular weight suitable for treatment in the polymerization phase ofthe cycle thus obs taining greater yields of liquid products than (lill.ISG-lili) have heretofore been obtained from a similar raw material.

Another object of my invention is to provide a unitary process for theconversion of normally gaseous hydrocarbons predominating in lowermolecular weight unsaturated hydrocarbons to normally liquid productswherein the normally gaseous hydrocarbons are treated to eiectconversion ofthe lower molecular weight unsaturated hydrocarbon tounsaturated hydrocarbons of higher molecular weight with thesimultaneous production of olen oxides, for example ethylene oxide,capable ofpromoting polymerization reactions and wherein normallygaseous hydrocarbons comprising the higher molecular weight unsaturatesand the olefin oxides produced therewith are subjected to conditions oftemperature and pressure whereby conversion of normally gaseoushydrocarbons to normally liquid, stable, gasoline-like products of highantiknock value is effected. f

My invention contemplates a process for the conversion in a continuousstream of normally gaseous hydrocarbons comprising substantial amountsof ethylene, or consisting essentially or principally of ethylene tonormally liquid products in the gasoline lboiling range, wherein thenormally gaseous hydrocarbons are treated, in the presence of a suitablepromoter toconvert ethylene to unsaturated hydrocarbons of highermolecular weight. The normally gaseous hydrocarbon stream comprising thehigher boiling unsaturates so produced is subjected to conditions oftemperature and pressure whereby normally gaseous hydrocarbons areconverted to normally liquid products in the gasoline boiling range. Theconversion products are fractionated to separate normally liquidproducts from the normally gaseous products. The normally gaseousreaction products are again fractionated to segregate a fractionpredominating in hydrocarbons having three or more carbon atoms to themolecule which may be recycled .to the thermal conversion zone. 'Iheremaining normally gaseous products comprising ethane, ethylene,hydrogen and methane are further fractionated to segregate a fractionpredominating in ethane and ethylene which is recycled to the primaryconversion zone wherein ethylene is converted to unsaturatedhydrocarbons of higher molecular weight. If desired the hydrocarbonfraction predominating in ethane and ethylene may be treated to effect aconcentration of the ethylene before recycling the traction to theprimary conversion zone.

the treatment of gases in which the concentration of ethylene isparticularly high. My invention, therefore, has the further advantage ofbeing able to operate on the effluent gases normally eliminated fromsome polymerization units because of theirl high ethylene content.

When charging those normally gaseousy hydrocarbons for which my-processis especially adapted, that is, those containing substantial amounts ofethylene, the hydrocarbons in admixture with controlled quantities of apromoting agent capable of converting ethylene to unsaturatedhydrocarbons of higher molecular weight are passed through a preheatingcoil and discharged into a reaction zone, under conditions which willeffect the conversion of ethylene to unsaturated hydrocarbons of highermolecular weight.

Suitable agents for promoting the conversion of ethylene to unsaturatedhydrocarbons ofhigher molecular weight are: oxygen or anoxygencontaining gas, halogens, sulfur or compounds of these elementssuch as SO2 or SaClz. Of these oxygen is preferred. When oxygen is usedas the activating agent there will be produced simultaneously with theconversion of ethylene to unsaturated hydrocarbons of higher molecularweight small quantities of oleiine. oxides, such as ethylene oxide,which are of especial value in promoting thel ,subsequent conversion ofnormally gaseous hydrocarbons to normally liquid products.

The invention will be more fully understood from the followingdescription read in connection with the accompanying drawing showingdiagrammatically an elevation of one form of apparatus for carrying outthe process of the invention.

Referring to the drawing, normally gaseous hydrocarbons predominatingdrawn through line I from an outside source, not shown, and forced bymeans of pump 2 through line I, controlled by valve 3, into a preheatingcoil 5 positioned in furnace '6. Prior to their entry into preheatingcoil 5, the hydrocarbon gases are mixed with an activating agent, forexample oxygen, supplied from an outside source, not shown, through lineI controlled by valve 8. The

quantity of oxygen added to the charge may vary between 0.5% and 3%, andshould preferably be about 1%, by volume of the charge passed into coil5. The stream of hydrocarbons with the admlxed oxygen is preheated incoil 5 to a temperature of approximately 750 to 1200 F., and at a lowpressure ranging from slightly above atmospheric to about pounds persquare inch. 'I'he preheated gaseous mixture leaving coil 5H is passedthrough line 9 into the reaction chamber I0 wherein the conditions oftemperature and pressure prevailing in coil 5 are maintained. Althoughin the specific example illustrating the invention the conversion ofetlwlene to unsaturated hydrocarbons of higher molecular weight iscarried out in a reaction chamber, the invention is in no wise limitedto the use of such reaction chamber, and the reaction may be effected ina separate coil or in a continuation of coil 5 itself. When the giventemperature and pressure conditions are carefully maintained in coil inethylene are 5 and reaction chamber I0, a substantial portion ofethylene, in the presence of the admixed oxygen, is converted inreaction chamber I0' to unsaturated hydrocarbons having three and fourcarbon atoms to the molecule. The gases are maintained in the reactionchamber I0 for a period of time sufliciently long to eiect the desiredconversion, which will normally not exceed about ten seconds. Themechanism of the reaction or reactions by which ethylene is converted inreaction chamber I0 to unsaturated hydrocarbons of higher molecularweight is not fully understood. It is probable that the presence of theoxygen promotes the disruption of the carbon to hydrogen linkages of theethylene in a manner the conversion of ethylene to unsaturatedhydrocarbons of higher molecular weight other promoters such ashalogens, sulphur or compoundsof these elements such as SO2 or SzClz maybe used. When, as in the present instance, oxygen is used as theactivating agent for the primary conversion operation there are formed,simultaneously with the higher molecular weight unsaturatedhydrocarbons, lesser quantities of oxygenated hydrocarbons comprisingolen oxides, for example, ethylene oxide, as well as small amounts ofhydrogen and oxides of carbon.

Reaction rproducts comprising the higher mo- .lecular weight unsaturatedhydrocarbons propylene and butylene, and the hydrogen and oxygenatedproducts produced. simultaneously therewith, comprising oleiin oxidessuch as ethyleneoxide, are withdrawn from reaction chamber I0 throughline II controlled by valve I2 and conducted to a heat exchanger I3wherein the products are cooled by indirect heat exchange with v asuitable cooling medium which may be fresh charge to the system.Additional cooling by means of indirect exchange not shown in thedrawing may be resorted to if desired. To enable compression of thegaseous stream to that pressure desired in the subsequent phase of theprocess the gases are cooled in heat exchanger I3 to a .temperature atwhich such compression can more easily be effected, for example, 300 to500 F. The cooled stream is conducted from exchanger I3 through line I4to compressor I5 wherein the` gases are brought to a pressure of from400 to 3000 lbs. and preferably about 1000 to 1500 lbs. from compressorI5 through lines I6 and I1 into conversion coil I8 positioned' infurnace I9 wherein the hydrocarbon stream is raised to a temperature of750.to 1250 F. and preferably from 900 to l050 F. to eect the conversionof normally gaseous hydrocarbons to normally liquid products in thegasoline boiling range. Normally gaseous hydrocarbons, substantiallyparafiinic in character, or containing both paraflins and olelns, may bedrawn from an'outslde source through line 20 controlled by valve 2| andforced by means of pump 22 into line I1 wherein they are mixed with theproducts resulting from the ethylene conversion operation. As analternative to their direct introduction into the system through line 20the normally gaseous hydrocarbons may, by means of connections not shownin the drawing, be preheated by passage through exchanger i3 and thepreheated gases introduced into line i'l. If desired, these additionalhydrocarbons may be preheated by direct admixture with the hot reactionproducts emanating from reaction chamber l and the resulting mixedstream passed to compressor l5. For example, these additionalhydrocarbons may be admixed with the hot products from chamber lll byintroduction through line 50, provided with valve lil, which connectswith line Il. The conversion of normally gaseous hydrocarbons tonormally liquid products eiected in conversion coil i3 may be, asdescribed, oi the thermal type involving both polymerization andalkylation rcactions although catalyst may be used to effect the desiredconversion. The presence, in the conversion coil i3, of olefin oxides,for example ethylene oxide, produced in reaction chamber lllsimultaneously with the conversion of ethylene to unsaturatedhydrocarbons of higher molecular weight, materially aids in promotingthe conversion of normally gaseous hydrocarbons to liquid products. Ifthe production of these olefin oxides in reaction chamber i3 should bebelow the quantity required for the desired promotional eect in thesubsequent thermal conversion phase of the process, or if they should becompletely absent due to the use of an activating agent other thanoxygen in reaction chamber l0', olefin oxides, such as ethylene oxide,may be supplied from an outside source through line 23 controlled byvalve 2li and admixed with the gaseous charge flowing through line il'to the conversion coil lll.

Reaction products pass from conversion coil i3 through line 23 and arecooled to below an 'active polymerization temperature by indirect heatexchange in exchanger 23. Additional cooling or quenching of reactionproducts in line 23 by means not shown in the drawing may be resorted toif desired. The cooled reaction products pass into a fractionator 2lwherein normally liquid products having a boiling point above that ofthe gasoline boiling range are separated and withdrawn from the bottomthrough line 33 controlled by valve 23. Uncondensed vapors and gases arepassed from the primary fractionator 3l through line 33 to fractionator3l wherein normally liquid products in the gasoline boiling range arecondensed and withdrawn from the -bottom of fractionator 3l through line32 controlled by valve 33. Normally gaseous reaction products comprisinghydrocarbons having less than ve carbon atoms to the molecule andhydrogen are passed from fractionator 3l through line 33 to anotherfractionator 33 wherein a fraction predominating in three and fourcarbon atoms to the molecule is segregated. This fraction is drawnromfractionator 35 through line 33 controlled by valve 3l and recycled tothe thermal conversion zone i3 by means of pump 3,3 which forces thefraction through line 33 into line l1. Normally gaseous reactionproducts not vcondensed in fractionator 35 and comprising ethane,ethylene, methane and hydrogen are passed from fraftionator 35 throughline t0 into fractionator 4l. a fraction predominating in ethane andethylene is segregated from the lighter gases comprising In fractionator4l methane and hydrogen which leave fractionator 4l through line 42controlled by valve 33 and are eliminated from the system. Thehydrocarbon fraction predorninating in ethane and ethylene in liquefiedcondition is drawn from fractionator 4l through line M and forced bymeans of pump 45 through line 56 into line 4 leading to the ethyleneconversion phase of the process. The ethylene-ethane fraction drawn fromfractionator 3l may be subjected to any desired treatment, not shown inthe drawing, whereby the ethylene in the fraction is concentrated beforebeing returned to the ethylene conversion stage of the cycle. Suchethylene concentration could be effected, for example, by absorption ofthe ethylene by a suitable absorbing medium such as acetone,acetaldehyde -or liquid acetylene with subsequent recovery of theabsorbed ethylene which is then returned to the ethylene conversionzone. i

Normally gaseous hydrocarbons predominat- J ing in or consistingessentially of ethylene are charged to the system, as has been pointedout above, through line l. If it is desired to process normally gaseoushydrocarbons comprising substantial proportions of hydrocarbons havingmore than two carbon atoms to the molecule, or

less than two carbon atoms to the vmolecule in addition to ethylene'thecharge may be introduced into the system through line lll controlled byvalve 33 and forced by means of pump 33 through line 50 intofractionator 33 to be subjected to fractionation therein together withthe Vnormally gaseous reaction products resulting from the thermalconversion operation.

Although in the specic example set forth to illustrate the invention theunsaturated hydrocarbons produced by the conversion of ethylene in theprimary conversion phase of the process are converted to normally liquidproducts "in a thermal conversion type of operation, 'it is to beunderstood that the process is not limited to the use of this particulartype of operation toeffect this phase of the process. The normallygaseous unsaturated hydrocarbons resulting from the conversion ofethylene into unsaturated hydrocarbons of higher molecular weight may beconverted to liquid products in a polymerization operation of thecatalytic type whereinthe normal gaseous hydrocarbonsV are subjected toa temperature of from 300 to 600 F., preferably about 400 to 500 F., anda pressure of 50 to 500 pounds, preferably 100 to 200 pounds in thepresence of an active polymerization catalyst such as phosphoric acid.While phosphoric acid is preferred, other catalysts such as aluminumchloride, alumina on silica, sodium aluminum' chloride, sulfuric acid orsimilar catalysts may be used.

The invention as set forth is particularly applicable to the conversion,in the primary phase of the process, of ethylene to unsaturatedhydrocarbons of higher molecular weight. 1 wishto point out that myprocess is not limited to the the conversion of this particularunsaturate ln this phase of the process and that, should it be desired,propylene or a higher unsaturate may be charged to the primaryconversion zone of the process in place of the ethylene, or togetherwith ethylene, to be converted to higher olefins without detracting fromthe effective operation `of the process according to the invention.

elli

j As pointed out above, the presence of the olen oxides, for exampleethylene oxide, formed simultaneously with thevhigher molecular weightunsaturated hydrocarbons in reaction chamber lll are of particular valuein promoting polymerization reactions either of the thermal or catalytictype. Furthermore, their presence in the systemlends to the normallyliquid polymers drawn from fractionator 3| through line 32 a high degreeof gum stability. Products of polymerization containing olefin oxidesmaybe mixed with cracked gasoline of a high unsaturate content andthemixture digested at a moderately high temperature, `for example, 400 to700 F., at a moderately high pressure, for example, 500 to 1000 poundsfor a sulcient period of time to effect the desired polymerization ofgum-forming constituents in the mixture. A small amount of olein oxides,for example, ethylene oxide from an outside source may be added to themixture of polymer and cracked gasoline to promote the completepolymerization of any potential gumforming compounds in the gasolineblend.

Obviously many modifications and variations of the invention, ashereinbefore set forth, may be made without departing from the spiritand scope thereof, and therefore only such limitations should be imposedas are indicated in the appended claims.

I claim:

1. The method of converting normally. gaseous hydrocarbons to normallyliquid` products which comprises subjecting an ethylene-rich gaseoushydrocarbon mixture in admixture with oxygen to elevated temperature ina primary conversion zone to eiect conversion of ethylene to normally Igaseous olefin hydrocarbons having more than two carbon atoms permolecule and olefin oxides, admixing the hot reaction products from saidprimary conversion zone with a gaseous hydr0- carbon mixture containinghydrocarbons having more than two carbon atoms per molecule to reducesubstantially the temperature of said reaction products, and subjectingthe resulting mixwherein the pressure maintained in said primary' Iconversion zone is not greater than from atmospheric to 100 pounds persquare inch, and the` pressure applied to the reaction products"therefrom is substantially greater.

3. The method of treating a hydrocarbongas mixture comprising ethyleneand hydrocarbons having at least three carbon atoms per molecule -whichcomprises treating said mixture to separate therefrom an ethylene-richfraction and a C3 fraction predomlnating in hydrocarbons having at leastthree carbon atoms per molecule, subjecting said ethylene-rich fractionin admixture with oxygen to elevated temperature in a primary conversionzone under conditions suitable to eiect conversion of ethylene tonormally gaseous olen hydrocarbons' having more than two carbon atomsper molecule and olen oxides, admixing the reaction products from saidprimary conversion zone with sald C3 fraction, and subjecting theresulting mixture' to elevated temperature whereby olefin oxides presenttherein promote conversion of normally gaseous hydrocarbon constituentsto normally liquid products. 4. The method in accordance with claim 3herein the reaction in said primary conversion zone is effected underrelatively low pressure, the

hot reaction products therefrom are admixed with said C3 fraction tosubstantially reduce the temperature of said reaction products, and theresulting mixture is subjected to elevated temperature at relativelyhigh pressure to effect production of normally liquid products.

HAROLD V. ATWELL.

